From bcbde4c0a7556cca72874c5e1efa4dccb5198a2b Mon Sep 17 00:00:00 2001 From: Julian Anastasov Date: Thu, 12 Sep 2013 11:21:07 +0300 Subject: ipvs: make the service replacement more robust commit 578bc3ef1e473a ("ipvs: reorganize dest trash") added IP_VS_DEST_STATE_REMOVING flag and RCU callback named ip_vs_dest_wait_readers() to keep dests and services after removal for at least a RCU grace period. But we have the following corner cases: - we can not reuse the same dest if its service is removed while IP_VS_DEST_STATE_REMOVING is still set because another dest removal in the first grace period can not extend this period. It can happen when ipvsadm -C && ipvsadm -R is used. - dest->svc can be replaced but ip_vs_in_stats() and ip_vs_out_stats() have no explicit read memory barriers when accessing dest->svc. It can happen that dest->svc was just freed (replaced) while we use it to update the stats. We solve the problems as follows: - IP_VS_DEST_STATE_REMOVING is removed and we ensure a fixed idle period for the dest (IP_VS_DEST_TRASH_PERIOD). idle_start will remember when for first time after deletion we noticed dest->refcnt=0. Later, the connections can grab a reference while in RCU grace period but if refcnt becomes 0 we can safely free the dest and its svc. - dest->svc becomes RCU pointer. As result, we add explicit RCU locking in ip_vs_in_stats() and ip_vs_out_stats(). - __ip_vs_unbind_svc is renamed to __ip_vs_svc_put(), it now can free the service immediately or after a RCU grace period. dest->svc is not set to NULL anymore. As result, unlinked dests and their services are freed always after IP_VS_DEST_TRASH_PERIOD period, unused services are freed after a RCU grace period. Signed-off-by: Julian Anastasov Signed-off-by: Simon Horman --- include/net/ip_vs.h | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) (limited to 'include/net/ip_vs.h') diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h index fe782ed2fe72..9c4d37ec45a1 100644 --- a/include/net/ip_vs.h +++ b/include/net/ip_vs.h @@ -723,8 +723,6 @@ struct ip_vs_dest_dst { struct rcu_head rcu_head; }; -/* In grace period after removing */ -#define IP_VS_DEST_STATE_REMOVING 0x01 /* * The real server destination forwarding entry * with ip address, port number, and so on. @@ -742,7 +740,7 @@ struct ip_vs_dest { atomic_t refcnt; /* reference counter */ struct ip_vs_stats stats; /* statistics */ - unsigned long state; /* state flags */ + unsigned long idle_start; /* start time, jiffies */ /* connection counters and thresholds */ atomic_t activeconns; /* active connections */ @@ -756,14 +754,13 @@ struct ip_vs_dest { struct ip_vs_dest_dst __rcu *dest_dst; /* cached dst info */ /* for virtual service */ - struct ip_vs_service *svc; /* service it belongs to */ + struct ip_vs_service __rcu *svc; /* service it belongs to */ __u16 protocol; /* which protocol (TCP/UDP) */ __be16 vport; /* virtual port number */ union nf_inet_addr vaddr; /* virtual IP address */ __u32 vfwmark; /* firewall mark of service */ struct list_head t_list; /* in dest_trash */ - struct rcu_head rcu_head; unsigned int in_rs_table:1; /* we are in rs_table */ }; -- cgit v1.2.1